Early Risers

Are you a morning person or a night owl? Whatever you are, it’s all in your genes. A fascinating new study suggests that early risers may have inherited genetic variants from the Neanderthals — who went extinct some 40,000 years ago — that increased the odds of their being morning rather than evening people.

The Study

While the human body clock is a complex trait shaped by social and cultural norms as well as genetics, Neanderthals, who evolved in higher latitudes in Europe and Asia for hundreds of thousands of years, may have been better adapted to seasonal variations in daylight than early Homo sapiens, or modern humans, according to a study published on Thursday in the journal Genome Biology and Evolution.

The study says early modern humans evolved in latitudes closer to the equator in Africa, where there is less variation in daylight hours. It is likely that adaptation to fluctuations in the amount of sunshine was passed down to early Homo sapiens as they travelled north out of Africa and encountered and interbred with Neanderthals.

Genes at Play

Prof. Gyaneshwar Chaubey, known for his work in biological anthropology, medical genetics and forensics, says that after the groundbreaking whole genome sequencing of the Neanderthals, it has been known that modern humans met them when they moved out of Africa. “This resulted in gene exchange between Neanderthals and our ancestors. The study explores the impact of interbreeding between modern humans and Neanderthals, on the evolution of circadian rhythm or chronotype,” explains the Professor attached to the Department of Zoology at the Banaras Hindu University.

To identify potential changes in circadian biology, researchers looked at the genetic sequences, splicing, and regulation of circadian genes in Neanderthals and modern humans.

Remarkably, the strongest effect of introgression (the transfer of genetic information from one species to another due to hybridisation) on chronotype resulted in an increase in ‘morningness’, suggesting an adaptive response to high latitudes. “This aligns with the idea that archaic introgression played a role in helping anatomically modern humans adapt to Eurasian environmental factors, such as reduced ultraviolet radiation and varied seasonal dynamics,” the Professor Chaubey shares. “These findings highlight how crucial the genetic contributions of ancient human beings have shaped present human circadian biology and environment adaptability,” he adds.

Cock-a-doodle Doo!

Offering a different perspective on the subject, Dr. Prashanth N Suravajhala, Principal Scientist, Systems Genomics, Amrita School of Biotechnology (Amrita Vishwavidyapeetham), Kerala, says while it is a very interesting study on how we inherit genes from Neanderthals, the circadian rhythm could also be attributed to the sub-population dynamics where “roosters and Neanderthals living in proximity obtained this ‘internal clock’ that follows the cycle of day and night.” He feels these habitual traits may have been transferred to the Neanderthals from the roosters, proving that genes are influenced by the environment. Elaborating, Dr Prashanth says “We could dig deeper for paleontological proof of sleeping patterns of Neanderthals and birds to explain this introgression.” In general, genetic variance across such sup-population dynamics is key to understanding more traits related to behaviour, habitat, genealogy, ancestry bias.

"The genetic variance across such sup-population dynamics is key to understanding more traits related to behaviour, habitat, genealogy, ancestry bias.” — Dr Prashanth N Survajhala of Amrita School of Biotechnology

"This study confirms our forefathers’ foresight in acquiring multiple helpful genes from archaic humans in order to adapt to the varied Eurasian environment.”— Prof. Gyaneshwar Chaubey, Banaras Hindu University

Body Clock

According to the study, “at higher latitudes, it is advantageous to have a body clock that is better able to anticipate and change to match changing seasonal light levels.”